Data Compression System for Liquid Crystal Display and Related Power Saving Method

ABSTRACT

A drive circuit applicable to a display device includes a first signal path and a second signal path. The first signal path, configured to receive image data and transmit the image data in a first operation mode, includes a compression unit, a storage unit and a de-compression unit. In the first operation mode, the compression unit performs a compression procedure on the image data to generate compression data, the storage unit stores the compression data, and the de-compression unit receives the compression data and performs a de-compression procedure on the compression data to recover the image data. The second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit in a second operation mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 14/078,490, filed on Nov. 12, 2013, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a data compression system for a liquid crystal display (LCD), and more particularly, to a data compression system and related power saving method capable of selecting a data transmission path according to an operation mode.

2. Description of the Prior Art

The liquid crystal display (LCD), which has advantages of thin appearance, low power saving and low radiation, etc. has widely been applied in various electronic products such as a computer screen, mobile telephone, personal digital assistant (PDA), flat television, and other communication/entertainment equipment. The principle of LCD is to vary the arrangement of liquid crystal molecules in a liquid crystal layer by varying the voltage difference between two terminals of the liquid crystal layer. The transparency of the liquid crystal layer may change accordingly, which is further incorporated with the light source provided by a backlight module to display images.

The LCD includes a drive chip. After data is transmitted from a host to the drive chip, the data may be compressed by a compression circuit and stored in a compression memory. The drive chip then utilizes a de-compression circuit to transmit the data to the display area. When the drive chip is operated in some particular modes, information related to complete color gamut may not be required. Thus, compressing the information data of complete color gamut via the compression circuit may generate unnecessary power consumption.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide a data compression system for a liquid crystal display (LCD), in order to reduce power consumption of the LCD.

The present invention discloses a drive circuit applicable to a display device. The drive circuit comprises a first signal path and a second signal path. The first signal path, configured to receive image data and transmit the image data in a first operation mode, comprises a compression unit, a storage unit and a de-compression unit. The compression unit is configured to perform a compression procedure on the image data to generate compression data in the first operation mode. The storage unit, coupleable to the compression unit, is configured to store the compression data in the first operation mode. The de-compression unit, coupled to the storage unit, is configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode. The second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit in a second operation mode.

The present invention further discloses a data compression system applicable to a display device. The data compression system comprises a host and a drive circuit. The host is configured for outputting image data. The drive circuit, coupled to the host, comprises a first signal path and a second signal path. The first signal path, configured to receive image data from the host and transmit the image data in a first operation mode, comprises a compression unit, a storage unit and a de-compression unit. The compression unit is configured to perform a compression procedure on the image data to generate compression data in the first operation mode. The storage unit, coupled to the compression unit, is configured to store the compression data in the first operation mode. The de-compression unit, coupled to the storage unit, is configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode. The second signal path is configured to receive image data from the host, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit in a second operation mode.

The present invention further discloses a power saving method. The power saving method comprises conducting a first signal path in a first operation mode, wherein the first signal path comprises a compression unit, a storage unit and a de-compression unit. The compression unit is configured to perform a compression procedure on image data to generate compression data in the first operation mode. The storage unit, coupled to the compression unit, is configured to store the compression data in the first operation mode. The de-compression unit, coupled to the storage unit, is configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode. The power saving method further comprises conducting a second signal path in a second operation mode, wherein the second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit.

The present invention further discloses a power saving method for a display device. The power saving method comprises performing a first signal processing procedure in a first operation mode. The first signal processing procedure comprises performing a compression procedure on image data to generate compression data in the first operation mode; storing the compression data in a storage device in the first operation mode; and performing a de-compression procedure on the compression data to recover the image data in the first operation mode. The power saving method further comprises performing a second signal processing procedure in a second operation mode. The second signal processing procedure comprises transmitting the image data to the storage unit so as to bypass the compression procedure; and transmitting the image data received from the storage unit to a display unit so as to bypass the decompression procedure.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a data compression system according to an embodiment of the present invention.

FIG. 2A and FIG. 2B are schematic diagrams of a data format according to an embodiment of the present invention.

FIG. 2C is a schematic diagram of compressed data according to an embodiment of the present invention.

FIG. 3 and FIG. 4 are timing diagrams of image data indifferent output terminals according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a data compression system according to another embodiment of the present invention.

FIG. 6 and FIG. 7 are timing diagrams of image data indifferent output terminals according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of a process according to an embodiment of the present invention.

FIG. 9 is a schematic diagram of a process according to an embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of a data compression system 10 according to an embodiment of the present invention. The data compression system 10 is utilized for a liquid crystal display (LCD). The data compression system 10 includes a host 100 and a drive circuit 120. The host 100 is utilized for outputting image data Img_D in a data format frmt1 or a data format frmt2 according to an operation mode of the LCD. Preferably, the drive circuit 120 may be realized by a drive integrated circuit (IC). The drive circuit 120 includes an image data unit 121, a compression unit 122, switching units 123 and 126, a storage unit 124, a de-compression unit 125, a display unit 127, a bypass path L1 and a complete data path L2. The switching units 123 and 126 are utilized for switching between the bypass path L1 and the complete data path L2. The compression unit 122 is utilized for receiving the image data Img_D and performing a compression procedure on the image data Img_D according to the operation mode to generate a compression data Cmprs_D. The storage unit 124, coupled to the compression unit 122 and the host 100, is utilized for storing the compression data Cmprs_D and the image data Img_D. The storage unit 124 may preferably be a static random access memory (SRAM). The de-compression unit 125, coupled to the storage unit 124, is utilized for receiving the compression data Cmprs_D and performing a de-compression procedure on the compression data Cmprs_D to recover the image data Img_D according to the operation mode. The display unit 127 is utilized for displaying the image data Img_D.

When the operation mode is a particular mode, the host 100 outputs the image data Img_D in a data format frmt1, and transmits the image data Img_D in the data format frmt1 via the bypass path L1. When the operation mode is a general mode, the host 100 outputs the image data Img_D in a data format frmt2, and transmits the image data Img_D in the data format frmt2 via the complete data path L2. Preferably, the image data in the data format frmt1 has fewer bit numbers than the image data in the data format frmt2. In addition, the particular mode includes a color gamut reduction mode, a partial area display mode and a scale up display mode. In the particular mode, the full information of the color gamut is not necessary. For example, in the color gamut reduction mode, RGB color model may be reduced from 24 bits to 3 bits; in the partial area display mode, when the LCD is switched from 480×800 full screen display to 100×100 partial screen display, other area on the screen that does not display images may be replaced by a single color; in the scale up display mode, when the LCD is switched from 480×800 full screen display to 240×400 scale up display, only half data is required to fulfill 480×800 full screen display. Therefore, in the particular mode, the host 100 may output the image data Img_D in the data format frmt1 with smaller data quantity, reduce the data quantity required to be stored in the storage unit 124, and transmit the image data Img_D to the display unit 127 via the bypass path L1 without undergoing the compression procedure and de-compression procedure. As a result, unnecessary power consumption will be prevented.

Please refer to FIGS. 2A, 2B and 2C. FIG. 2A is a schematic diagram of the data format frmt2 according to an embodiment of the present invention; FIG. 2B is a schematic diagram of the data format frmt1 according to an embodiment of the present invention; FIG. 2C is a schematic diagram of the compression data Cmprs_D according to an embodiment of the present invention. In FIG. 2A, each pixel includes three sub-pixels R, G, B, and each sub-pixel may be represented by 8 bits. Therefore, each pixel includes 24 bits. In FIG. 2B, each pixel only uses 3 bits to represent three sub-pixels R, G, B. In comparison, the data format frmt1 has less data quantity than the data format frmt2.

The operations of the data compression system 10 are detailed as follows. When the operation mode is the general mode, the host 100 outputs the image data Img_D in the data format frmt2. The image data Img_D in the data format frmt2 may first be passed through the image data unit 121, and then transmitted to the compression unit 122 via the complete data path L2. The compression unit 122 performs the compression procedure on the image data Img_D in the data format frmt2 to generate the compression data Cmprs_D. The switching unit 123 selects the compression data Cmprs_D coming from the complete data path L2, and stores the compression data Cmprs_D in the storage unit 124. The de-compression unit 125 then receives the compression data Cmprs_D, and performs the de-compression procedure on the compression data Cmprs_D to recover the image data Img_D in the data format frmt2. The switching unit 126 transmits the image data Img_D in the data format frmt2 to the display unit 127 via the complete data path L2. Finally, the display unit 127 displays the image data Img_D in the data format frmt2. When the operation mode is switched from the general mode to the particular mode, the host 100 re-transmits transmitted image data Prv_D1 in the data format fmrt1 in the next image frame after the switching, where the transmitted image data Prv_D1 has been transmitted in the data format fmrt2 when the operation mode is the general mode. When the host 100 re-transmits the image data Prv_D1 in the data format fmrt1, the display unit 127 displays a black screen, in order to prevent an abnormal image from being displayed. When the operation mode is the particular mode, the host 100 outputs the image data Img_D in the data format frmt1. The image data Img_D in the data format frmt1 first is passed through the image data unit 121, and transmitted to the switching unit 123, bypassing the compression unit 122 via the bypass path L1. The switching unit 123 selects the image data Img_D in the data format frmt1 coming from the bypass path L1, and stores the image data Img_D in the data format frmt1 in the storage unit 124. The switching unit 126 then transmits the image data Img_D in the data format frmt1 to the display unit 127 via the bypass path L1. Finally, the display unit 127 displays the image data Img_D in the data format frmt1. When the operation mode is switched from the particular mode back to the general mode, the host 100 re-transmits an image data Prv_D2 in the data format fmrt2 in next image frame after the switching, and the image data Prv_D2 has been transmitted in the data format fmrt1 when the operation mode is the particular mode. When the host 100 re-transmits the image data Prv_D2 in the data format fmrt2, the display unit 127 displays a black screen, in order to prevent an abnormal image from being displayed. The operations after the operation mode returns to the general mode are illustrated above, and will not be narrated herein. Therefore, when the operation mode is the particular mode, the data compression system 10 transmits the image data Img_D in the data format fmrt1 to the display unit 127 via the bypass path L1 and omits the compression procedure and the de-compression procedure, in order to reduce power consumption.

In addition, please refer to FIG. 3 and FIG. 4. FIG. 3 is a timing diagram of image data in different output terminals when the operation mode is switched from the general mode to the particular mode according to an embodiment of the present invention; FIG. 4 is a timing diagram of image data in different output terminals when the operation mode is switched from the particular mode to the general mode according to an embodiment of the present invention. In FIG. 3 and FIG. 4, the horizontal axis represents time, on which each time interval denotes a time period of an image frame. Details of FIG. 3 and FIG. 4 are illustrated above, and will not be narrated herein.

Please refer to FIG. 5, which is a schematic diagram of a data compression system 50 according to another embodiment of the present invention. The data compression system 50 may be utilized in an LCD. The basic structures of the data compression system 50 are similar to those of the data compression system 10; hence data in the same output terminals are denoted by the same symbols. The data compression system 50 includes a host 500 and a drive circuit 520. The host 500 is utilized for outputting an image data Img_D, which is in a data format fmrt2. Preferably, the drive circuit 520 may be realized by a driving IC. The drive circuit 520 includes an image data unit 521, a compression unit 522, switching units 523 and 527, a storage unit 524, a format conversion unit 525, a de-compression unit 526, a display unit 528, a bypass path L3 and a complete data path L4. The switching units 523 and 527 are utilized for switching between the bypass path L3 and the complete data path L4. The compression unit 522 is utilized for receiving the image data Img_D and performing the compression procedure on the image data Img_D to generate the compression data Cmprs_D according to the operation mode. The storage unit 524, coupled to the compression unit 522 and the host 500, is utilized for storing the compression data Cmprs_D and the image data Img_D. Preferably, the storage unit 524 may be an SRAM. The format conversion unit 525, coupled to the storage unit 524, is utilized for performing a format conversion procedure to convert the image data Img_D into the data format frmt1 or the data format frmt2. The de-compression unit 526, coupled to the storage unit 524, is utilized for receiving the compression data Cmprs_D and performing the de-compression procedure on the compression data Cmprs_D to recover the image data Img_D according to the operation mode. The display unit 528 is utilized for displaying the image data Img_D.

When the operation mode is the particular mode, the image data Img_D in the data format frmt2 is transmitted to the storage unit 524 via the bypass path. The format conversion unit 525 reads the image data Img_D in the data format frmt2 from the storage unit 524, converts the image data Img_D in the data format frmt2 into the data format frmt1 with smaller amount of data, and stores the data back to the storage unit 524, where the compression procedure and the de-compression procedure are both omitted. As a result, unnecessary power consumption may be prevented.

The operations of the data compression system 50 are detailed as follows. When the operation mode is the general mode, the host 500 outputs the image data Img_D in the data format frmt2. The image data Img_D in the data format frmt2 is first passed through the image data unit 521, and transmitted to the compression unit 522 via the complete data path L4. The compression unit 522 performs the compression procedure on the image data Img_D in the data format frmt2 to generate the compression data Cmprs_D. The switching unit 523 selects the compression data Cmprs_D from the complete data path L4, and stores the compression data Cmprs_D in the storage unit 524. The de-compression unit 526 then receives the compression data Cmprs_D, and performs the de-compression procedure on the compression data Cmprs_D to recover the image data Img_D in the data format frmt2. The switching unit 527 transmits the image data Img_D in the data format frmt2 to the display unit 528 via the complete data path L4. Finally, the display unit 528 displays the image data Img_D in the data format frmt2. When the operation mode is switched from the general mode to the particular mode, the host 500 outputs the image data Img_D in the data format frmt2 to the image data unit 521, and transmits the image data Img_D in the data format frmt2 to the storage unit 524 via the bypass path L3. The format conversion unit 525 reads the image data Img_D in the data format frmt2 from the storage unit 524 in the next image frame after the switching, and converts the image data Img_D from the data format frmt2 into the data format frmt1 and then stores the image data Img_D back to the storage unit 524. When the format conversion unit 525 performs the format conversion procedure, the display unit 528 displays a black screen, in order to prevent an abnormal image from being displayed. When the format conversion procedure is accomplished, the display unit 528 may display the image data Img_D in the data format frmt1. When the operation mode is switched from the particular mode back to the general mode, the format conversion unit 525 reads the image data Img_D in the data format frmt1 from the storage unit 524 in the next image frame after the switching, and converts the image data Img_D from the data format frmt1 into the data format frmt2 and then stores the image data Img_D back to the storage unit 524. Similarly, when the format conversion unit 525 performs the format conversion procedure, the display unit 528 may display a black screen, in order to prevent an abnormal image from being displayed. When the format conversion procedure is accomplished, the display unit 528 may display the image data Img_D in the data format frmt2. The operations after the operation mode returns to the general mode are illustrated above, and will not be narrated herein. Therefore, when the operation mode is the particular mode, the data compression system 50 transmits the image data Img_D to the display unit 528 via the bypass path L3, and the compression procedure and the de-compression procedure are omitted, in order to reduce power consumption. Please note that, in comparison with the data compression system 10, in the data compression system 50 the host 500 may not need to re-transmit, and the data format conversion is performed by the format conversion unit 525.

In addition, please refer to FIG. 6 and FIG. 7. FIG. 6 is a timing diagram of image data in different output terminals when the operation mode is switched from the general mode to the particular mode according to an embodiment of the present invention; FIG. 7 is a timing diagram of image data in different output terminals when the operation mode is switched from the particular mode to the general mode according to an embodiment of the present invention. In FIG. 6 and FIG. 7, the horizontal axis represents time, on which each time interval denotes a time period of an image frame. Details of FIG. 6 and FIG. 7 are illustrated above, and will not be narrated herein.

The operations related to the data compression system 10 can be summarized into a process 80, as shown in FIG. 8. The process 80, which may be utilized in the data compression system 10 for power saving, includes the following steps:

Step 800: Start.

Step 802: Determine the operation mode. If the operation mode is the general mode, go to Step 804; if the operation mode is the particular mode, go to Step 806.

Step 804: Output the image data Img_D in the data format fmrt1, and go to Step 808.

Step 806: Output the image data Img_D in the data format fmrt2, and go to Step 810.

Step 808: Transmit the image data Img_D in the data format fmrt1 via the bypass path L1, and go to Step 816.

Step 810: Transmit the image data Img_D in the data format fmrt2 via the complete data path L2.

Step 812: Perform the compression procedure.

Step 814: Perform the de-compression procedure.

Step 816: Display the image data Img_D.

According to the process 80, when the operation mode is the particular mode, the data compression system 10 transmits the image data Img_D in the data format fmrt1 via the bypass path L1 and omits the compression procedure and the de-compression procedure, in order to reduce power consumption. When the operation mode is the general mode, the data compression system 10 performs the compression procedure and the de-compression procedure on the image data Img_D in the data format fmrt2 via the complete data path L2. Detailed operations of the process 80 are illustrated above, and will not be narrated herein.

The operations related to the data compression system 50 can be summarized into a process 90, as shown in FIG. 9. The process 90, which may be utilized in the data compression system 50 for power saving, includes the following steps:

Step 900: Start.

Step 902: Output the image data Img_D, wherein the image data Img_D has the data format frmt2.

Step 904: Determine the operation mode. If the operation mode is the general mode, go to Step 906; if the operation mode is the particular mode, go to Step 908.

Step 906: Transmit the image data Img_D in the data format fmrt2 via the bypass path L3, and go to Step 914.

Step 908: Transmit the image data Img_D in the data format fmrt2 via the complete data path L4.

Step 910: Perform the compression procedure.

Step 912: Perform the de-compression procedure, and go to Step 916.

Step 914: Perform the format conversion procedure.

Step 916: Display the image data Img_D.

According to the process 90, when the operation mode is the particular mode, the data compression system 50 transmits the image data Img_D in the data format fmrt2 via the bypass path L3 and omits the compression procedure and the de-compression procedure, and performs the format conversion procedure to convert the image data Img_D from the data format fmrt2 into the data format fmrt1. When the operation mode is the general mode, the data compression system performs the compression procedure and the de-compression procedure on the image data Img_D in the data format fmrt2 via the complete data path L4. Detailed operations of the process 90 are illustrated above, and will not be narrated herein.

To sum up, an embodiment of the present invention may determine a transmitting path of the image data (the bypass path or the complete data path) according to the operation mode. When the operation mode is the particular mode without full color information (the color gamut reduction mode, the partial area display mode and the scale up display mode), an embodiment of the present invention may transmit the image data in a data format with smaller amount of data or convert the image data into a data format with smaller amount of data to transmit the image data via the bypass path, wherein the compression procedure and the de-compression procedure are omitted, in order to achieve power saving.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. A drive circuit applicable to a display device, comprising: a first signal path, configured to receive image data and transmit the image data in a first operation mode, comprising: a compression unit, configured to perform a compression procedure on the image data to generate compression data in the first operation mode; a storage unit, coupleable to the compression unit, configured to store the compression data in the first operation mode; and a de-compression unit, coupled to the storage unit, configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode; and a second signal path, configured to, in a second operation mode, receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit.
 2. The drive circuit of claim 1, wherein in the first operation mode, the image data received by the compression unit is in a first format and in the second operation mode, the image data received by the second signal path is in a second format having fewer bit numbers than the image data in the first format.
 3. The drive circuit of claim 2, further comprising a format conversion unit, coupled to the storage unit, configured to perform a format conversion procedure to convert the image data received from the storage unit into the first format in the second operation mode, and not to perform the format conversion procedure in the first operation mode.
 4. A data compression system applicable to a display device, comprising: a host, for outputting image data; and a drive circuit, coupled to the host, comprising: a first signal path, configured to receive image data from the host and transmit the image data in a first operation mode, comprising: a compression unit, configured to perform a compression procedure on the image data to generate compression data in the first operation mode; a storage unit, coupled to the compression unit, configured to store the compression data in the first operation mode; and a de-compression unit, coupled to the storage unit, configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode; and a second signal path, configured to, in a second operation mode, receive image data from the host, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit.
 5. The data compression system of claim 4, wherein in the first operation mode, the image data received by the compression unit is in a first format and in the second operation mode, the image data received by the second signal path is in a second format having fewer bit numbers than the image data in the first format.
 6. The data compression system of claim 5, further comprising a format conversion unit, coupled to the storage unit, configured to perform a format conversion procedure to convert the image data received from the storage unit into the first format in the second operation mode, and not to perform the format conversion procedure in the first operation mode.
 7. A power saving method comprising: conducting a first signal path in a first operation mode, wherein the first signal path comprises: a compression unit, configured to perform a compression procedure on image data to generate compression data in the first operation mode; a storage unit, coupled to the compression unit, configured to store the compression data in the first operation mode; and a de-compression unit, coupled to the storage unit, configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode; and conducting a second signal path in a second operation mode, wherein the second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit.
 8. The power saving method of claim 7, wherein in the first operation mode, the image data received by the compression unit is in a first format and in the second operation mode, the image data received by the second signal path is in a second format having fewer bit numbers than the image data in the first format.
 9. The power saving method of claim 8, further comprising performing a format conversion procedure to convert the image data received from the storage unit into the first format in the second operation mode, and not performing the format conversion procedure in the first operation mode.
 10. A power saving method for a display device comprising: performing a first signal processing procedure in a first operation mode, wherein the first signal processing procedure comprises: performing a compression procedure on image data to generate compression data in the first operation mode; storing the compression data in a storage device in the first operation mode; and performing a de-compression procedure on the compression data to recover the image data in the first operation mode; and performing a second signal processing procedure in a second operation mode, wherein the second signal processing procedure comprises: transmitting the image data to the storage unit so as to bypass the compression procedure; and transmitting the image data received from the storage unit to a display unit so as to bypass the decompression procedure.
 11. The power saving method of claim 10, wherein in the first operation mode, the image data processed by the compression procedure is in a first format and in the second operation mode, the image data processed by the second signal processing procedure is in a second format having fewer bit numbers than the image data in the first format.
 12. The power saving method of claim 11, further comprising performing a format conversion procedure to convert the image data received from the storage unit into the first format in the second operation mode, and not performing the format conversion procedure in the first operation mode. 